The study of genetic variation in many organisms has achieved central importance in the study of human diseases and organismal developmental biology. In human genetics recent emphasis is on detection and assay of new genetic polymorphisms (single nucleotide, polymorphisms, SNPs) which are necessary for research on inherited diseases, both mono- and polygenic. In the last three years, our program project has contributed a new method for discovery of new polymorphisms, DHPLC (Denaturing High Performance Liquid Chromatography) which has the unique advantages of accuracy, sensitivity, speed as well as being a highly automated process. With this method, we have detected a large number of biallelic SNPs on autosomes, mtDNA and the Y chromosome. The Y chromosome and mtDNA studies have proved differences between male and female transmission, with unexpected evolutionary consequences. These studies will be extended to the X chromosome, and compared with autosomal variation. We plan to do this by testing the large number of new polymorphisms being detected by the NHGRI, or by our Program Project, in DNA segments of known sequence and special interest. By- products of this research will be: 1) a comparative test of new methods of studying in large numbers of individuals the new polymorphism of interest, 2) the definition of batches of genetic markers most useful for evolutionary analysis, 3) the accumulation of data on such polymorphisms in diverse populations which will improve our knowledge of the history of human evolution, and will also help clarify the role and the relative influence of drift and natural selection. This last point is especially timely, as a collection of cell lines representing the world's population is being accumulated at CEPH (the Center for the Study of Human Polymorphism). CEPH will make DNA available to research workers in order to generate a new database in collaboration with the Human Genome Diversity Project. Its organization will be very similar to that with which CEPH generated the human chromosomes linkage map. Our collaborative work of the last few years has also developed methods for evolutionary dating using microsatellites, and/or SNPs, a task that we will further develop. This was made possible by the collaboration between molecular geneticists and theoretical population geneticists in the last five years of the program project. This collaboration will be continued, and in addition we plan to strengthen methods of analysis of genome variation.